The present invention relates to a power steering apparatus and, more particularly, to a backlash adjustment mechanism arranged in the power steering apparatus to reduce backlash in a worm gear.
Japanese Laid-Open Patent Publication No. 2004-345444 discloses a conventional type of power steering apparatus that includes a steering mechanism for transmitting a driver's steering force to steerable wheels, an electric motor for applying a torque as a steering assist force and a worm gear for transmitting the torque of the electric motor to the steering mechanism. The worm gear has, in a gear housing, a worm shaft rotatably mounted on a ball bearing and a worn wheel engaged with the worm shaft so as to reduce the motor torque and transmit the reduced motor torque to the steering mechanism.
This power steering apparatus further includes an annular elastic body disposed on the worm gear as a backlash adjustment mechanism. The annular elastic body is held in a deformed state between the gear housing and the ball bearing and exerts an elastic force (restoring force) on the worm shaft in accordance with the amount of deformation thereof so as to bias the worm shaft toward the worm wheel, bring gear teeth of the worm shaft into engagement with gear teeth of the worm wheel and thereby reduce backlash between the gear teeth of the worm shaft and the gear teeth of the worm wheel.